The present invention relates to a constituent parts assembling method for an actuating apparatus which includes a plurality of constituent parts and produces an output in response to an input signal, and more particularly relates to a technique being preferably applicable to an actuating apparatus (e.g., an injector of a fuel injection apparatus) which includes numerous mechanical constituent parts and accordingly inherently possesses the output characteristics being not easily adjustable through electric adjustment only.
One representative example of the actuating apparatuses including numerous mechanical constituent parts is an accumulator fuel injection system.
For example, a well-known injector incorporated in an accumulator fuel injection system is a 2-way valve type which includes a control chamber provided at a non-injection side of a control piston accommodated in this injector and an electromagnetic valve for open/close controlling a passage connecting the control chamber to depressurized fuel (i.e., a fuel discharge side) to drive a needle valve as well as the control piston, thereby controlling the fuel injection timing.
According to this type of injector, if necessary, an inlet orifice (i.e., an inflow orifice) and an outlet orifice (i.e., an outflow orifice) are provided at a fuel inflow side and a fuel outlet side of the control chamber, respectively. The fuel pressure in the control chamber reduces in response to valve open of the electromagnetic valve, and the lift movement of the control piston and the needle valve causes fuel injection.
In recent years, purifying exhaust gas emissions is strictly required and accordingly the requirement to reduce the difference in injection characteristics among individual injectors is increasing.
Hence, an identification pattern is given to each injector in accordance with individual injection amount characteristics. Such an identification pattern is indicated somewhere on each injector so that an electronic control unit driving and controlling this injector can read this information before or after the injector is installed on the engine. The electronic control unit corrects the injection amount characteristics of respective injectors with reference to their identification patterns so as to eliminate individual differences of the injectors, as disclosed in the Japanese Patent Application No. 7-32142 and in WO97/20136 (corresponding to the Japanese Tokuhyo No. 2000-501155).
However, the correction of the electronic control unit disclosed in the above-described prior art is performed by picking up several points on a three-dimensional map defined by fuel pressure, injection pulse, and injection amount. When the correction point excurses or deviates out of the map, it is difficult to sufficiently correct the injection amount differences caused due to individual differences of respective injectors.
Furthermore, the items that can be corrected by the electronic control unit are limited to the injection amount and the injection timing in response to the injection command. The injection rate and the injection period of the injector could not be corrected.
In other words, according to the conventional technique, to obtain a predetermined injection amount, the electronic control unit corrects the injection period to become long when the corrected injector has a low injection rate as its characteristics. On the other hand, to obtain same injection amount, the electronic control unit corrects the injection period to become short when the corrected injector has a high injection rate as its characteristics. Accordingly, the required exhaust gas purification function cannot be attained satisfactorily.